Folded longitudinal torsional hinge for gimbaled MEMS mirror

Abstract

In a gimbaled micromachined micromirror array optimized for parallel-plate electrostatic operation, longitudinal-type gimbal hinge elements are provided in which a plurality of torsional longitudinal hinge elements are arranged in an array parallel to the axis of rotation and which are linked together by rigid lateral brace sections. In primary embodiment the hinge elements are arranged in a double gimbal configuration. Specific embodiments of the hinge elements are simple longitudinal, compound longitudinal, stacked simple longitudinal, and stacked compound longitudinal. The longitudinal hinges may be used with various types of mirrors including circular or rectilinear, recessed or nonrecessed, where the hinges are connected in either a symmetric or asymmetric configuration relative to one another, as hereinafter illustrated by way of a subset of examples. A preferred embodiment of a mirror structure suitable for an array structure according to the invention is a nonstacked compound longitudinal hinge symmetrically connected to a circular nonrecessed electrostatically-actuatable parallel plate mirror within a substantially circular ring hinged in substantially the same way to form a double gimbaled structure.

1. A double-gimbaled micromachined mirror structure for parallel-plate electrostatic operation, said mirror structure comprising:
 a substrate of a micromirror array with embedded electrostatic electrodes;  
 a mirror in said array of said substrate;  
 a gimbal around said mirror; and  
 a plurality of folded longitudinal gimbal hinge structures such that a plurality of torsional hinge elements are disposed in parallel orientation to the axis of rotation of each hinge structure, said folded longitudinal gimbal hinge structures being disposed at four positions on a gimbal ring, a first pair of said folded longitudinal gimbal hinge structures connecting said mirror to said gimbal and a second pair of said folded longitudinal gimbal hinge structures connecting said substrate to said gimbal.  
 
   
   
     2. The apparatus according to  claim 1  wherein each said folded longitudinal gimbal hinge structure is compound. 
   
   
     3. The apparatus according to  claim 1  wherein each said folded longitudinal gimbal hinge structure is simple. 
   
   
     4. The apparatus according to  claim 1  wherein each said folded longitudinal gimbal hinge structure is disposed symmetrically with respect to an opposite hinge structure. 
   
   
     5. The apparatus according to  claim 1  wherein each said folded longitudinal gimbal hinge structure disposed asymmetrically with respect to an opposite hinge structure. 
   
   
     6. The apparatus according to  claim 1  wherein said mirror is round. 
   
   
     7. The apparatus according to  claim 1  wherein each said folded longitudinal hinge structure is formed of stacked folded longitudinal hinges. 
   
   
     8. The apparatus according to  claim 1  wherein said folded longitudinal gimbal hinge structures attached to the gimbal are recessed into the mirror. 
   
   
     9. In a double-gimbaled micromachined mirror structure for parallel-plate electrostatic operation, a simple gimbal hinge at four positions on a gimbal ring, each simple gimbal hinge comprising:
 a plurality of torsional hinge elements arranged in an array parallel to a longitudinal axis of rotation, said hinge elements being linked together in serpentine fashion by rigid braces at ends of said hinge elements;  
 a first external connection point disposed off-center from the lateral edge of the array on a first side of the longitudinal axis of rotation; and  
 a second external connection point disposed off-center from the lateral edge of the array on a second side of the longitudinal axis of rotation.  
 
   
   
     10. The apparatus according to  claim 9  wherein:
 said hinge elements are of the same thickness as said rigid braces;  
 said hinge elements have an aspect ratio of thickness to the width of the rigid braces of at least one; and wherein  
 said hinge elements are of a length which is substantially greater than width and height of each said binge element.  
 
   
   
     11. The apparatus according to  claim 9  further including shock compensation gaps between selected adjacent moveable elements and etch compensation material in said hinge elements and said rigid braces. 
   
   
     12. The apparatus according to  claim 9  wherein said first external connection point of a first simple gimbal hinge is connected on the same side of said longitudinal axis as said first external connection point of a second opposing simple gimbal hinge to form a symmetrically connected gimbal mirror structure. 
   
   
     13. The apparatus according to  claim 9  wherein said first external connection point of a first simple gimbal hinge is connected on the opposite side of said longitudinal axis as said first external connection point of a second opposing simple gimbal hinge to form an asymmetrically connected gimbal mirror structure. 
   
   
     14. The apparatus according to  claim 9  wherein said hinge structures attached between the mirror and the gimbal are recessed into the mirror. 
   
   
     15. In a double-gimbaled micromachined mirror structure for parallel-plate electrostatic operation, a simple gimbal hinge at four positions on a gimbal ring, each simple gimbal hinge comprising:
 a plurality of torsional hinge elements arranged in an array parallel to a longitudinal axis of rotation, said hinge elements being linked together in serpentine fashion by rigid braces at ends of said hinge elements;  
 a first external connection point disposed on a first cantilever element at the longitudinal axis of rotation; and  
 a second external connection point disposed on a second cantilever element at the longitudinal axis of rotation on an opposing side of said array.  
 
   
   
     16. The apparatus according to  claim 15  wherein a plurality of said simple gimbal hinges is joined at said connection points in series along said longitudinal axis to form a stacked hinge structure. 
   
   
     17. The apparatus according to  claim 15  further including shock compensation gaps between selected adjacent moveable elements and etch compensation material in said hinge elements and said rigid braces. 
   
   
     18. In a double-gimbaled micromachined mirror structure for parallel-plate electrostatic operation, a stacked gimbal hinge structure at four positions on a gimbal ring, each stacked gimbal hinge structure comprising:
 a first gimbal hinge, said first gimbal hinge including: 
 a first plurality of torsional hinge elements arranged in a first array parallel to a longitudinal axis of rotation, said first hinge elements being linked together in serpentine fashion by first rigid braces at first ends of said first hinge elements;  
 a first external connection point disposed on a first cantilever element at the longitudinal axis of rotation; and  
 a second external connection point disposed on a second cantilever element at the longitudinal axis of rotation on an opposing side of said first array; and  
 
 a second gimbal hinge, said second gimbal hinge including: 
 a second plurality of torsional hinge elements arranged in a second array parallel to the longitudinal axis of rotation, said second hinge elements being linked together in serpentine fashion by second rigid braces at third ends of said second hinge elements;  
 said third external connection point being disposed on said third cantilever element at the longitudinal axis of rotation; and  
 a fourth external connection point disposed on a fourth cantilever element at the longitudinal axis of rotation on an opposing side of said second array;  
 
 wherein said external connection point is at said third external connection point and said third cantilever element is an extension of said second cantilever element.  
 
   
   
     19. The apparatus according to  claim 18  wherein each said gimbal hinge is compound. 
   
   
     20. The apparatus according to  claim 18  wherein each said gimbal hinge is simple. 
   
   
     21. In a double-gimbaled micromachined mirror structure for parallel-plate electrostatic operation, a compound gimbal hinge at four positions on a gimbal ring, each compound gimbal hinge comprising:
 a first plurality of first torsional hinge elements arranged in a first array parallel to a longitudinal axis of rotation, said first hinge elements being linked together in serpentine fashion by first rigid braces at ends of said first hinge elements;  
 a second plurality of second torsional hinge elements arranged in a second array parallel to the longitudinal axis of rotation, said second hinge elements being linked together in serpentine fashion by second rigid braces at ends of said second hinge elements;  
 a U-shaped brace connected at a first end to said first array and at said second end to said second array for form a compound hinge structure;  
 a first external connection point to the first array disposed adjacent to and on a first side of the longitudinal axis; and  
 a second external connection point to the second array disposed at the lateral edge of the second array on a second side of the longitudinal axis.  
 
   
   
     22. The apparatus according to  claim 21  wherein a plurality of said compound gimbal hinges is joined at said connection points in series along said longitudinal axis to form a stacked hinge structure. 
   
   
     23. The apparatus according to  claim 21  further including shock compensation gaps between selected adjacent moveable elements and etch compensation material in said hinge elements and said rigid braces. 
   
   
     24. The apparatus according to  claim 21  wherein said first external connection point of a first compound gimbal hinge is connected on the same side of said longitudinal axis as said first external connection point of a second opposing compound gimbal hinge to form a symmetrically connected gimbal mirror structure. 
   
   
     25. The apparatus according to  claim 21  wherein said first external connection point of a first compound gimbal hinge is connected on the opposite side of said longitudinal axis as said first external connection point of a second opposing compound gimbal hinge to form an asymmetrically connected gimbal mirror structure. 
   
   
     26. The apparatus according to  claim 21  with etch compensation wherein selected ones of said rigid braces have a width greater than adjacent elements. 
   
   
     27. The apparatus according to  claim 17  with etch compensation wherein selected ones of said rigid braces have a width greater than adjacent elements. 
   
   
     28. The apparatus according to  claim 23  with etch compensation wherein selected ones of said rigid braces have a width greater than adjacent elements.